linux-kernel - Re: [patch V3 57/66] x86/pkru: Remove xstate fiddling from write

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Message-ID: <YNIaq1VDpeV33BEo@zn.tnic>
Date:   Tue, 22 Jun 2021 19:15:23 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [patch V3 57/66] x86/pkru: Remove xstate fiddling from
 write_pkru()

On Fri, Jun 18, 2021 at 04:19:20PM +0200, Thomas Gleixner wrote:
> The PKRU value of a task is stored in task->thread.pkru when the task is
> scheduled out. PKRU is restored on schedule in from there. So keeping the
> XSAVE buffer up to date is a pointless exercise.
> 
> Remove the xstate fiddling and cleanup all related functions.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/include/asm/pkru.h          |   17 ++++-------------
>  arch/x86/include/asm/special_insns.h |   14 +-------------
>  arch/x86/kvm/x86.c                   |    4 ++--
>  3 files changed, 7 insertions(+), 28 deletions(-)

Yap, untangling PKRU from XSAVE makes the related code a lot nicer, I
gotta say.

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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